GENERAL SUMMARY 381 



thick-walled spores, (3) thousands of thin-walled gemmae, and (4) a very 

 tough fatty matrix. 



The projectile of Sphaerobolus stellatus is very adhesive and its spores 

 and gemmae are not dispersed by either wind or rain. 



The structure of the Sphaerobolus stellatus fruit-body has been 

 redescribed with the aid of photomicrographs and drawings. The 

 peridium, as found by Miss Walker, consists of six layers : (1) mycelial 

 hyphae surrounding the exterior of the sporocarp, (2) a gelatinous layer, 

 (3) a pseudoparenchymatous layer, (4) a fibrous layer made up of inter- 

 woven largely tangential hyphae, (5) a palisade layer becoming pseudo- 

 parenchymatous over the top of the sporocarp, and (6) a thin layer of 

 pseudoparenchyma surrounding the gleba. 



The fruit-body of Sphaerobolus stellatus opens stellately. The rim of 

 the cup, owing to continual expansion of the highly turgid palisade layer, 

 gradually increases in diameter and bends outwards. When a certain 

 stage in the process has been reached, the palisade layer and the fibrous 

 layer, which act as everting membranes, yield to the strain which has 

 been set up and suddenly turn inside out, thus slinging the glebal mass 

 away. After discharge of the glebal mass, the everted membranes 

 have a balloon-like appearance ; and they are usually left standing over 

 the cup, attached to its teeth, and covering the orifice. 



The force which brings about the discharge of the Sphaerobolus gun 

 is located in the inner everting membranes ; for, if these are removed 

 from the outer non-everting membranes and are placed on a moist surface 

 in a damp-chamber or are submerged in water, they evert and cast away 

 the projectile. 



The expansion of the palisade layer, which leads eventually to the 

 eversion of this layer and of the fibrous layer, is caused by the lateral 

 swelling of the individual palisade cells. During this swelling, the 

 glycogen in the cells is converted into sugar. 



When from an opened fruit-body the glebal mass is removed and in its 

 place is substituted a small pebble, a lead shot, a ball of paraffin wax, or 

 a drop of mercury, these objects are eventually cast out of the fruit-body 

 in the same way as the glebal mass would have been. 



The tooth-tip mode of attachment of the inner everting set of 

 membranes to the outer non-everting set of membranes is such that the 

 inner set of membranes, when everting, is given the maximum possible 

 working distance for pressing against the projectile. It is this long work- 

 ing distance — about 3 mm. — which in a large degree is responsible for 

 the high efficiency of the Sphaerobolus gun. 



The diamond-shaped openings which are formed laterally between the 

 everting and the non-everting sets of membranes as eversion takes place 

 allow air to rush into the central cavity and so prevent an internal vacuum 

 coming into existence and interfering with the efficient working of 

 the gun. 



